Gears and Cam: an Essential Mechanism to download and make.
Members and Patrons can download the parts for free, non-members can join in the fun for £2.50 at the link. The 4:1 reduction gear makes the cam shaft turn nice and slow giving plenty of time for the cams to tell an interesting story. Use this project as exercise in pure mechanism or as the starting point for your own animated paper characters.

Print the parts pages onto thin card. (230gsm / 67lb) I used coloured card for a colourful model but you could use white card or card printed with a pattern design.

The gears and cams are made from double thickness card for added strength and durability. Fold them in half and glue them down making sure that tabs are not glued. Once the glue is dry carefully cut them out.

Make up the box sides, the triangular sections are right angle triangles. To ensure that the rectangle section is accurately made fold it flat as it is glued them fold it back into position.

Make up the other side with right angle triangle tubes.

The top and base are strengthened with equilateral triangle tubes.

Glue the top and base to the side with the rectangle tube. Note where the large cut outs are aligned.

Glue on the other side

Fold round and glue closed the box then glue down the flaps front and back ensuring that the box remains square.

Roll up and glue down the two axle tubes. Line up the ends as accurately as possible with the small triangles.

Glue the small end stop of the pinion axle.

Thread the pinion axle into place from inside the box.

Assemble the handle in three steps.

Fit the pinion to the handle. I left mine unglued to allow fine adjustments to positioning.

Glue the handle to the pinion shaft.

Glue the axle stub up through the back of the large gear then glue down the four flaps.

Glue the two cams to the cam shaft, line them up with the grey lines.

Position the large gear on the box then thread the long axle down through the axle stub…

…and through the camshaft so that it protrudes through the other side of the box. No glue needed, this is a friction fit.

The two gears should now mesh up nicely. You may need to move the pinion gear slightly for best effect.

Assemble the two cam followers

Assemble the two cam follower ends.

Glue the cam follower ends to the underside of the cam followers as shown.

Fit the cam followers into the box.

Make up the two push rods from double thickness card.

Thread the push rods down through the box top and glue them to the cam followers.

Ta daa! Turn the handle and the large gear turns slowly driving the cam shaft to tell its story.